A device for preventing vertical oscillations of the elevator car during standstill phases has become known from EP 1 067 084 B1. The device has a brake caliper, which can be pressed against the guide rails via a compound lever mechanism. Brake shoes are disposed on the front ends of the brake caliper lever. This device causes a more or less rigid securing of the car to the guide rails as a result of friction. It has been shown, however, that in practice such securing devices place high demands on control and regulating technology. In particular, it is difficult, or complicated, respectively, to operate the elevator in such a manner that it is possible to smoothly initiate movement of the car after it has been at a standstill.
Instead of securing devices, it is also possible to achieve a sufficiently pleasant feeling of comfort for the passengers during a standstill of the car if the vertical oscillations of the car are simply damped, or reduced, for which purpose significantly smaller forces are required. A damping unit for reduction of vertical oscillations of the car during standstill phases is demonstrated, by way of example, in EP 1 424 302 A1. The damping unit exhibits a lever arm, extending over approximately half of the depth of the car, on the free end of which a pivotally supported brake shoe is disposed. The damping unit is mechanically coupled to a door opening unit for the car; this damping unit, which can be activated by the drive unit for the door, requires complicated lever and gear mechanism mechanics, for which reason this solution is expensive and prone to malfunction. The device also cannot be retrofitted to already existing, older elevator facilities. Another disadvantage is that the damping characteristics of the car do not satisfy higher demands regarding operational comfort and reliability.
An assembly for the reduction of vertical oscillations of an elevator car during a standstill is known from WO 2011/021064 A1, with which brake shoe retainers centrally attached in an articulated manner to a lever arm can be moved against the guide rails by means of a cylinder powered by an electric motor, wherein the lever arms are pivotally adjoined at their lower ends to a base plate attached to a component of the car frame. The electric motor cylinder, installed in a transverse manner, is connected in an articulated manner to the opposing upper ends of the lever arms. The lever arms, provided with brake shoes, must be pivoted back and forth by means of the electric motor cylinder in order to alternate between the active position and the resting position. Both lever arms have a two-piece design, wherein the respective lever arm components can each be pushed against one another via a spring-supported damping mechanism comprising a helical compression spring. Undesired vertical oscillations during a car standstill are difficult to eliminate with this assembly, this being possible only with a high expenditure in terms of the control technology. Aside from the complicated construction, the assembly is also expensive and heavy. There is also the disadvantage that the assembly requires a lot of space.